Question

I am in need to replace

\\\s+\\$\\$ to $$

I used

String s = "  $$";
s = s.replaceAll("\\s+\\$\\$","$$");

but it throws exception

java.lang.IllegalArgumentException: Illegal group reference

Answer 1

Use "\\$\\$" in the second parameter:

String s="  $$";
s=s.replaceAll("\\s+\\$\\$","\\$\\$");
//or
//s=s.replaceAll("\\s+\\Q$$\\E","\\$\\$");

The $ is group symbol in regex’s replacement parameter

So you need to escape it